Radioactive measuring system for blast furnace charge location



Aug. 13, 1963 J. E. REIDER 3,100,841 RADIOACTIVE MEASURING SYSTEM FOR BLAST FURANCE CHARGE LOCATION F iled Sept. 25, 1959 2 Sheets-Sheet 1 COKE ,ORE,8\ LIMESTONE CRITICAL I" ZON E Aug. 13, 1963 J. E. RE IDER RADIOACTIVE MEASURING SYSTEM FOR BLAST FURANCE CHARGE LOCATION Filed Sept. 25, 1959 2 Sheets-Sheet 2 awash Patented Aug. 13, 1963 ice .RADIOACTIVE MEASURINGSYSTEM FOR BLAST This invention relates to level detectors and more particularly to novel method and means for determining the location of charge in a blast furnace. I

In the iron-making industry, iron ore, limestone and coke are converted to iron by a blast furnace. Within the blast furnace, the charge thereof comprises a column of these materials extending upwardly for substantially the height of the furnace. Heated air admitted at the base of the furnace rises by convection through the charge. A temperature gradient from 400 F. at the top of the furnace to 3000" at the base establishes a thermal column wherein the charge is heated to various temperatures at dilferent levels. In the upper half of the furnace, gas released from the coke removes oxygen from the iron ore. About midway down the furnace, the limestone begins to crumble and react with the impurities in the ore and coke to form molten slag. Near the base of the furnace, the intense heat liquefies the iron. The molten slag absorbs the ash of the burned coke and floats above a pool of liquidous iron. Periodically, the iron is tapped off into metal cars.

Charges of iron ore, limestone and coke are continually dumped into the top of the furnace by skip cars to replenish the materials used by the furnace. The upper twenty feet of the blast furnace comprises a critical 'zone in which the charge must be evenly distributed to insure proper pre-heating of the materials. However, variations in the physical and chemical characteristics of the input ingredients combined with the turbulence of the rising gases produce irregularities in the compaction of the charge. Holes or voids exist where the charge has not settled. In addition, the level of the charge in the furnace must be maintained to provide a thermal column of sufficient length to permit the thermochemical reactions to take place at the desired rate.

Due to the inaccessibility of the interior of the blast furnace, it is presently difficult to know the level of charge andimpossible to detect bridging and voids of the same. Accordingly, the addition of raw materials to the furnace has been controlled heretofore in a hit-and-rniss fashion. The blast furnace is either over-charged or not charged to a minimum level and voids are not detected and eliminated. The maximum efiiciency of operation is not extracted from the process.

In accordance with the present invention, a plurality of radiation sources and detectors are spaced vertically on the exterior shell of the blast furnace at various levels in the critical zone. Each detector is positioned to receive only radiation flux directed across the blast furnace by a source located in the same horizontal plane. An indicator is connected to each detector and energized to either of two alternate states to indicate either the presence or the absence of charge at that level.

Accordingly, it is a primary object of the present invention to provide a novel method and means for determining the location of charge in a blast furnace.

It is another object of the present invention to provide apparatus for determining voids and bridging in the charge of a blast furnace.

it is another object of the present invention to provide apparatus which is inexpensive to construct and economical to maintain.

. It is still another object of the present invention to provide apparatus capable of reliable operation in a hazardous atmosphere.

It is yet another object of the present invention to provide apparatus which enables more efiicient operation of a blast furnace than heretofore possible.

These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the drawings, in which:

FIG. 1 is a partially sectioned perspective view of a blast furnace illustrating a preferred embodiment of the present invention;

FIG. 2 is an enlarged partial side View of the blast furnace of FIG. 1, partly diagrammatic, showing one scheme for accomplishing the purposes of the present invention;

FIG. 3 is an enlarged sectional view of the blast furnace of FIG. 1 showing typical mounting details for a radiation source and detector;

FIG. 4 is another side view of the blast furnace of FIG. 1 showing an alternate arrangement of radiation sources and detectors; and

FIG. 5 is a schematic diagram of a representative circuit means operable to energize a level indicator.

With reference to the drawings and specifically to FIG. 1, a blast furnace it is shown having a charge 12 of coke, iron ore and limestone. These materials are poured into the blast furnace through a receiving hopper :14. To heat the furnace a bustle pipe 16 surrounds the base of the blast furnace It) and tuyeres 18 extend downwardly from the bustle pipe '16 to communicate with the interior'of the blast furnace. A hot air blast is continuously supplied to the bustle pipe 16 at 20 to fire the charge 12. Gases are generated as the heated air passes upwardly through the charge 12. Vents 22 carry these gases away from the top of the blast furnace 1d.

The charge 1 2 is continuously fired by the hot air admitted through the tuyeres 18 to produce molten iron 24 at the bottom of the blast furnace 10. Since the process is continuous, it is necessary to add material at 14 as more iron is produced. As noted on the drawing, the temperature of the charge 12 varies from ca. 400 F. at the top of the furnace to 3000 at the bottom. The temperature of the charge in the upper portion of the blast furnace 10 should be a predetermined minimum value and should increase uniformly toward the base. Pre-heating of the charge occurs in a critical zone extending down Wardly approximately twenty feet from the top of the blast furnace It). The temperature in this Zone is an important factor governing the efficiency of blast furnace operation. If the level of charge is too low, pre-heating of the charge 12 proceeds too swiftly. When the furnace is overcharged, pro-heating proceeds much too slowly to say nothing of the potentially hazardous condition which would exist if the vents 22 became blocked by the charge 12. In addition, the charge often develops voids 12a and bridging which disrupts the uniformity of charge distribution and interferes with the proper pie-heating of the charge. Heretofore, operating personnel had no way to determine the level of. the charge, voids or bridging.

Now referring to FIG. 2, the present invention provides a plurality of radiation level gauges 3039 each comprising a nuclear source of radiation 30a, a dectector 30b and an indicator light 39c located on an operator s control panel 40. The radiation sources 3lia39a are collinearily spaced in vertical alignment along one side of the blast furnace 1-0. The sources are spaced apart to direct individual beams of radiation through the critical zone.

The radiation from each source is directed in a concentrated beam toward a diametrically opposed detector mounted in the same horizontal plane. Each detector 30b39b is responsive only to radiation from its associated source by means of collimating devices described in detail hereinafter. Each detector is coupled to a trigger circuit housed in the control panel 40. Each trigger circuit controls the operation of one of the indicator lights 30c-39c.

In the. operation of the present invention, radiation energy trave'rsingthe blast furnace at a given level will be attenuated by the presence of the charge 12. The decrease in radiation intensity at the detector is noted as a drop in response. Decreased detector response permits the indicator light associated With that detector to be energized as described hereinafter in reference to FIG. 5. On the other hand, in the absence of charge at a particular level, intense irradiation of the detector occurs and the indicator light is extinguished. So, by observing the control board 40, an operator may be continuously advised of the level and distribution of charge 12 the critical zone of the blast furnace 10.

A typical scheme for mounting one source and detector unit is shown in FIG. 3. Referring to FIG. 3, the walls of the blast furnace comprise a heat-resistant lining 42 of refractory brick enclosed on the outside by a steel shell 44. At a predetermined level in the critical zone, a

, pair of diametrically opposed holes 46 are bored horizontally partially into the walls to reduce the mass of brick 42 seen by the source and detector to a minimum. A

cylindrical thermocouple Well 48 is inserted in each of the bored holes. Each pair of thermocouple wells 48 located in the same horizontal plane is positioned in axial alignment and welded to the steel shell 44.

Over one of the thermocouple wells, a source housing 50 is bolted to the steel shell 44. Housing 50 is prefena'bly fabricated of lead for purposes of shielding and constructed with a recess 52 also in axial alignment with the well 48. A source capsule 54 is positioned in the bottom of the recess 52. The source capsule 54 may contain any of the commercially available radioisotopes providing penetrative radiation, e.'g., cesium 137. Other feav tures such as a radiation shutter may be provided, but in a the interest of clarity, no illustration or description of this apparatus is provided herein.

The detector comprises a Geiger-Mueller tube 60 insulatively mounted in apipe 62. The G-M tube 60 is positioned adjacent the well opening to receive radiation passing therethrough. A clamp 64 serves to secure the detector assembly to the exterior shell 44. Although the G-M tube is shown mounted horizontally, it should be noted it may also be mounted vertically. It is only required that the sensitive wall area of the tube be exposed to the radiations of the diametrically opposed source.

During the normal operation of the blast furnace 10, it is not uncommon for the brick wall 42 to rise and fall according to the expansion and cooling of the surrounding environment. To prevent misalignment of the collimating wells 48, the holes 46 may be overbored to allow the well 46 to ride vertically therein. And, since both sides of the furnace experience the same magnitude and direction of vertical displacement, continuous axial align ment of the individual collimating wells is assured.

In the above apparatus, due to the substantial separa tion of each source and detector, a highly active source must be used to produce a detectable flux field in the vicinity of the G-M tube. In addition, only the core of the charge 12 is inspected with this arrangement. A modification of the present invention is shown in FIG. 4 whereby the source size may be considerably reduced and the charge 12 may be more thoroughly examined. With reference now to FIG. 4, a downwardly spiraling arrangement of source-detector units is employed. The radiation sources 30u39a are preferably radially separated by 1r/ 2 radians from one level to the next and equally vertically separated to cover the critical zone. Each detector is mounted on a horizontal chord of the blast furnace 10 in alignment with its associated source so that radiation is transmitted a much shorter distance than illustrated in FIG. 2. With this method, a larger representative crosssection of the charge 12 is examined and the chances of not .detecting a void are substantially eliminated.

' G-M tube 30b and the integrating network 80.

In the absence of an absorbing medium between the source 30a and G-M tube 3%, intense radiation strikes the G-M tube and the impedance of the G-M tube decreases. The resultant flow of current causes a rise in potential at the grid of the thyratron 70'. 'Ihyratron 70 is triggered into conduction to energize relay 72 when the firing potential is attained.

The indicating lamp 300 initially connected to a battery 86 by the normally closed contacts 72a and 72b of the plate relay is extinguished to indicate a void in the charge 12. However, if the charge 12 exists at the level of the source and detector units, thyratron 70 is cut off and the lamp 300 burns on the control panel 40 The grid potential necessary to fire the thyra-tron 7 0 depends on the bias adjustment of cathode potentiometer 76. The. adjustment at 76 controls the sensitivity of the indicator circuit, i.e., the mass cross-section of charge 12 required to change the indicator 30c from one state to the alternate.

It should be understood that the point of novelty of the present invention does not reside in the use of a fixed number of source-detector units. Accordingly, the number of source-detector units employed may vary from one to twenty depending on the thoroughness of examination desired. While a single unitindicates the presence or absence of charge at a given level, several should be em ployed to adequately examine the critical zone. In addition to the above departure from the illustrated embodiment, many other modifications may be made therein by adding, deleting, or omitting one or more of the component parts without detracting from the original spirit and scope of the present invention or sacrificing any of the advantages attendant thereto.

What is claimed is:

1. Apparatus for locating the charge in a blast furnace comprising means for directing a horizontal beam of radiation into said blast furnace at each of a plurality of downwardly spiraling points located at different levels above the base of said furnace, means for quantitatively detecting the amount of radiation transmitted through said furnace at each of said dilferent levels, and means for registering an indication whenever said detected radiation at any of said levels exceeds a predetermined value.

2. Apparatus for locating the charge within a critical zone of a cylindrical blast furnace comprising means for directing a plurality of beams of penetrating radiation into said furnace at a plurality of downwardly spiraling points within said zone, means for confining each of said beams to a diiferent horizontal plane corresponding to one of said points within said zone, means for quantitatively .detecting the amount of radiation transmitted through said furnace in each of said horizontal planes, and means for registering avisual indication in accordance with the relative position of each of said horizontal planes in said zone whenever said detected radiation exceeds a predetermined value in any of said horizontal planes.

3. Measuring apparatus for locating the charge in a cylindrical blast furnace comprising a plurality of radiation sources, an equal number of radiation detectors, means for mounting each of said radiation sources on the outside of said furnace at .a different horizontal plane, means for angularly separating sources located on ald."

joining horizontal planes, means for mounting each of said radiation detectors on said furnace at each of said horizontal planes in diametric opposition to each of said radiation sources to detect radiation transmitted across said furnace in said same horizontal plane, a plurality of indicators each energizable to one of two alternate states, and trigger circuit means connected between each of said detectors and each of said indicators to energize said indicater to the same state whenever said detected radiation in any of said horizontal planes exceeds a predetermined value.

4. Measuring apparatus for locating the charge in cylindrical blast furnace comprising a plurality of sources of a penetrative beam of nuclear radiation, an equal number of G-M tubes, means for mounting each of said radiation sources on the outside of said furnace at a different horizontal plane, means for angularly separating sources located in adjoining horizontal planes, means for mounting one of said G-M tubes on the outside of said furnace at each of said horizontal planes in diametric opposition to each of said radiation sources (to detect radiation transmitted across said furnace in said same horizontal plane, means in said radiation beam between each of said radiation sources and each of said detectors to confine said radiation beam to a substantially horizori-tal plane, a plurality of indicators each energizable to one of two alternate states, and trigger circuit means connected between each of said G-M tubes and each of said indicators to energize said indicator to the same state whenever said detected radiation in any of said horizontal levels exceeds a predetermined value.

5. Measuring apparatus for locating the charge in a cylindrical blast furnace having outwardly concentric walls of refractory brick and steel comprising a plurality of sources of a penetrative beam of nuclear radiation, an equal number of G-M tubes, a plurality of pairs of axially aligned recesses extending in a downward spiral about the central axis of said furnace, each of said pairs of recesses being provided at diiferent horizontal planes, means for mounting each of said radiation sources in registration with one recess of each of said pairs, means for mounting each of said G-M tubes in registration with the other recess of said pairs to detect radiation transmitted across said furnace by said source, a plurality of indicators each energizable to one of two alternate states, trigger circuit means connected between each of said G-M tubes and each of said indicators to energize said indicator to the same state whenever said detected radiation in any of said horizontal planes exceeds a predetermined value.

6, Measuring apparatus for locating the charge in a cylindrical blast furnace comprising a plurality of sources of a penetrative beam of nuclear radiation, an equal number of G-M tubes, means for mounting each of said radiation sources on the outside of said furnace at a different horizontal plane, means for angularly separating radiation sources located on adjoining horizontal planes, means for mounting one of said G-M tubes on the outside of said furnace at each of said horizontal planes in quadrature relationship with said source to detect radiation transmitted tangentially across said furnace by said source, and means for indicating when the detected radiation in any of said horizontal planes exceeds a predetermined value.

7. Measuring apparatus for locating the charge in a cylindrical blast furnace comprising a plurality of sources of a penetrative beam of nuclear radiation, an equal number of G-M tubes, means for mounting each of said radiation sources on the outside of said furnace at a different horizontal plane, means for angularly separating radiation sources located on adjacent horizontal llevels, means for mounting one of said G-M tubes on the outside of said furnace at each of said horizontal planes in quadrature relationship with said source to detect radiation [transmitted tangentially across said furnace by said source, collimating means between each of said sources and detectors to confine said radiation beam in any of said planes to a substantially horizontal chord of said furnace, a plurality of indicators each energizable to one of two alternate states, andtrigger circuit means connected between each of said G-M tubes and each of said indicators to energize said indicator to the same state whenever said detected radiation in any of said horizontal levels exceeds a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,534,352 Herzog Dec. 19, 1950 2,674,695 Grace Apr. 6, 1954 2,734,136 Atchison Feb. 7, 1956 2,737,592 Ohmart Mar. 6, 1956 2,776,377 Anger Jan. 1, 1957 2,933,601 Friedman Apr. 19, 1960 FOREIGN PATENTS 1,050,215 France Jan. 6, 1954 OTHER REFERENCES Gamma Density Controls Extraction Column, by B. G. Ryle, from Chemical Engineering Progress, vol. 53, No. 11, November 1957, pp. 551 to 555. 

1. APPARATUS FOR LOCATING THE CHARGE IN A BLAST FURNACE COMPRISING MEANS FOR DIRECTING A HORIZONTAL BEAM OF RADIATION INTO SAID BLAST FURNACE AT EACH OF A PLURALITY OF DOWNWARDLY SPIRALING POINTS LOCATED AT DIFFERENT LEVELS ABOVE THE BASE OF SAID FURNACE, MEANS FOR QUANTITATIVELY DETECTING THE AMOUNT OF RADIATION TRANSMITTED THROUGH SAID FURNACE AT EACH OF SAID DIFFERENT LEVELS, AND MEANS FOR REGISTERING AN INDICATION WHENEVER SAID DETECTED RADIATION AT ANY OF SAID LEVELS EXCEEDS A PREDETERMINED VALUE. 